This invention relates to a carbon black modified by a two step process in which carbon black is initially treated with functional monomers by an electropolymerization process to form a functionalized carbon black having an initial polymer attached to, of grafted to, the carbon black following which
(A) at least one diene monomer, or
(B) living anionic catalysis prepared polymer, is introduced to the functionalized carbon black to continue the polymerization, starting from a living end of the initially formed polymer, and thereby form an extended diene-based polymer. By the addition of the diene monomer or the live anionic polymer to form the associated extended diene-based polymer, it is contemplated that the modified carbon black is rendered more compatible with diene-based elastomers. Such modified carbon black may be used, for example, as reinforcement for component(s) of various articles of manufacture, including tires. Accordingly, an article of manufacture is provided, such as for example a tire, having at least one component of a rubber composition which contains such modified carbon black.
Preparation of a modified carbon black by an electropolymerization process may be accomplished, for example, by providing a suspension of carbon black particles and/or carbon black fibers in a suitable solvent and causing electropolymerization of functional monomers onto the surface of such carbon black
Exemplary of such process is seen in WO 99/02614 and WO 99/20697 patent publications.
However, it is contemplated herein that, where it is intended that such modified carbon blacks be used to reinforce various diene-based elastomers, such carbon blacks can be further modified to enhanced their usefulness for blending with diene-based elastomers.
In the description of this invention, the term xe2x80x9cphrxe2x80x9d where used herein, and according to conventional practice, refers to xe2x80x9cparts of a respective material per 100 parts by weight of rubber, or elastomerxe2x80x9d.
The terms xe2x80x9crubberxe2x80x9d and xe2x80x9celastomerxe2x80x9d if used herein, may be used interchangeably, unless otherwise prescribed. The terms xe2x80x9crubber compositionxe2x80x9d, xe2x80x9ccompounded rubberxe2x80x9d and xe2x80x9crubber compoundxe2x80x9d, if used herein, are used interchangeably to refer to xe2x80x9crubber which has been blended or mixed with various ingredients and materialsxe2x80x9d and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
In accordance with this invention, an electropolymerization surface modified carbon black is prepared by a method which comprises the steps of treating carbon black particles and/or carbon black fibers by:
(A) Forming a functional polymer by electropolymerization onto the surface of carbon black selected from at least one of carbon black particles and carbon black fibers by treating a dispersion of said carbon black particles and/or carbon black fibers in a combination of a monomer and solvent by introducing a negatively charged cathode and a positively charged anode individually to said dispersion with an electrical potential said cathode and anode to cause an electropolymerization of said monomer to form a living polymer (ionic or radicalar) on the surface of said carbon black particles and/or fibers, wherein said monomer and solvent combination is selected from;
(1) combination of monomer xe2x80x9cXxe2x80x9d and solvent selected from acrylic and methacrylic solvents, or
(2) monomer xe2x80x9cYxe2x80x9d and aprotic solvent, followed by
(B) introducing at least one polymerizable monomer to the living ends of said functional polymer formed on the surface of said carbon black particles and/or carbon black fibers of step (A) in said solvent solution and polymerizing said polymerizable monomer thereon in the presence of an anionic catalyst, and preferably in the presence of an anionic polymerization randomizing modifier, to form an elastomeric extension to said functional polymer carbon black particles and/or functionalized carbon black fibers, or
(C) quenching a living, anionic catalysis organic solution prepared elastomer by introducing said functionalized carbon black particles and/or functionalized carbon black fibers of said step (A) to said living elastomer, wherein said living elastomer is prepared by polymerizing at least one polymerizable monomer in the presence of an anionic catalyst, and preferably in the presence of an anionic catalyst modifier, to thereby form an elastomeric extension to said functionalized carbon black particles and/or said functionalized carbon black fibers, and
(D) recovering said treated carbon black particles and/or carbon black fibers;
wherein said solvent for said electropolymerization contains an electrolyte for providing a suitable electrical conductivity for the organic solvent solution for the electric current to effectively flow between said anode and said cathode;
wherein said polymerizable monomers for said step (B) and step (C) are selected from at least one of
(1) isoprene and 1,3-butadiene, and
(2) a combination of at least one of isoprene and 1,3-butadiene together with at least one of styrene and alphamethyl styrene, preferably styrene;
wherein said anionic catalysis prepared elastomer is preferably selected from cis 1,4-polybutadiene, cis 1,4-polyisoprene, isoprene/butadiene copolymer and styrene/isoprene/butadiene terpolymer,
wherein said combination of monomer xe2x80x9cXxe2x80x9d and solvent is a combination selected from acrylonitrile/acetonitrile, acrylonitrile/propylene carbonate, acrylonitrile/dimethylformamide, acrylonitrile/dimethacrylamide, acrylonitrile/pyridine, ethylacrylate/dimethylformamide, acrylonitrile/dimethacrylamide, ethylacrylate/pyridine, silyated-2-hydroxyethylmethacrylate/dimethylformamide, methylmethacrylate/dimethylformamide, glycidylmethacyrlate/dimethylformamide, n-butylacrylate/dimethylformamide, ter-butylacrylate/dimethylformamide, allylmethacrylate/dimethylformamide, pyrrole/dimethylformamide, thiophene/dimethylformamide and vinylpiridine/dimethylformamide; and
wherein said combination of monomer xe2x80x9cYxe2x80x9d and solvent is a combination selected from acrylonitrile/acetonitrile, acrylonitrile/dimethylacetamide, acrylonitrile/N,Nxe2x80x2-dimethylformamide, acrylonitrile/pyridine, ethylacrylate/N,Nxe2x80x2dimethylformamide, ethylacrylate/pyridine, trimethylsiloxyethylmethacrylate/N,Nxe2x80x2dimethylformamide, methylmethacrylate/N,Nxe2x80x2dimethylformamide, ter-butylacrylate/N,Nxe2x80x2dimethyhlformamide, glycidylmethacrylate/N,Nxe2x80x2dimethyhlformamide, n-butylacrylate/N,Nxe2x80x2dimethylformamide, allylmethacrylate/N,Nxe2x80x2dimethylformamide, pyrrole/dimethylformamide, thiophene/dimethylformamide and vinylpiridine/dimethylformamide.
It is to be appreciated that, for said electropolymerization of monomers onto the surface of said carbon black particles and/or carbon black fibers, the electrolysis bath also typically contain an electrolyte for a purpose of providing a suitable electrical conductivity for the organic solvent solution to enable the electric current to effectively flow from one electrode to the other and to cause the electrochemical reaction to proceed (electrical current flow between the aforesaid anode and cathode, as the case may be). A typical example of an electrolyte is tetraethyl ammonium perchlorate.
In practice, said anionic catalysis prepared elastomers can be prepared by polymerizing said polymerizable monomer(s) in an organic solvent in the presence of an anionic catalyst such as, for example, a butyl lithium catalyst, for which an anionic polymerization modifier is used for randomizing the prepared elastomer such as, for example, tetranethylene diamine (TMEDA) which is understood to be a typical modifier, for example, for butyl lithium catalysis of 1,3-butadiene to from a relatively randomized cis 1,4-polybutadiene.
Significant aspects of two step procedure for the invention is that in addition to
(A) first forming a functionalized carbon black by forming what is considered herein to be a significant covalent linkage between an electropolymerization formed first polymer and the carbon black particles and/or carbon black fibers, followed by
(B) forming an extended polymer thereon of an elastomer by
(1) a continued anionic polymerization of introduced polymerizable monomer(s) to provide a composite thereof with enhanced compatibility with diene based elastomers for which the treated carbon black can provide reinforcement, or
b) a quenching of polymerizate of an elastomer of anionic catalyzed monomers of at least one of 1,3-butadiene, isoprene, optionally with styrene in a form of at least one living elastomer, preferably as cis 1,4-polybutadiene, cis 1,4-polyisoprene, isoprenelbutadiene copolymers and styrene/isoprene/butadiene terpolymers to form a composite of said functionalized carbon black (functionalized carbon black particles and/or functionalized carbon black fibers) and elastomer. Such elastomer extended functionalized carbon black composite is envisioned herein as having an enhanced compatibility with, and thereby enhanced reinforcement of, diene-based elastomers when blended therewith.
Use of the treated bond carbon black of this invention, with the aforesaid covalent linkage between carbon black and elastomer and associated improved carbon black and elastomer interaction, for reinforcement of various rubber compositions, is considered herein to be particularly beneficial for enhancement of various physical properties of various rubber composition as compared to use of untreated carbon black. For example, such reinforcement is contemplated to be particularly beneficial for various tire components such as, a tire tread, including one or more of reduced tire tread wear and/or reduced rolling resistance for a tire tread.
It is to be appreciated that an electrical current resulting from the electrical potential between the cathode and anode causes a the electropolymerization to proceed. While in practice a direct current (DC) may be preferred, it is considered that, where appropriate, an alternate current (AC) might be used.
In additional accordance with this invention, an electropolymerization modified carbon black is provided by the method of this invention.
In further accordance with this invention, an electropolymerization modified carbon black-containing rubber composition is provided which comprises, based upon parts by weight of an ingredient per 100 parts by weight of elastomer (phr);
(A) 100 phr of at least one diene-based elastomer
(B) about 20 to about 150, alternately about 35 to about 115, phr of at least one reinforcing particulate filler as:
(1) about 20 to about 100, alternately about 30 to about 80, phr of said electropolymerization modified carbon black,
(2) from zero to about 50, alternately about 5 to about 35, phr of at least one additional particulate reinforcing material selected from carbon black, synthetic amorphous silica, starch/plasticizer composite, and silica treated carbon black having silica domains on its surface wherein said silica and silica of said silica treated carbon black contain hydroxyl groups (e.g. silanol groups) in its surface, and
(C) a coupling agent for said silica and silica treated carbon black as the case may be, wherein said coupling agent contains a moiety reactive with said hydroxyl groups on the surface of said silica and silica treated carbon black, as the case may be, and another moiety interactive with at least one of said elastomer(s).
In further accordance with this invention, an article of manufacture is provided having at least one component comprised of
(A) a rubber composition which contains said electropolymerization modified carbon black or
(B) said electropolymerization modified carbon black-containing rubber composition.
In additional accordance with this invention, a tire is provided having at least one component comprised of
(A) a rubber composition which contains said electropolymerization modified carbon black or
(B) said electropolymerization modified carbon black-containing rubber composition.
In further accordance with this invention, a tire is provided having a circumferential tread comprised of
(A) a rubber composition which contains said electropolymerization modified carbon black or
(B) said electropolymerization modified carbon black-containing rubber composition.